1. Field of the Invention
The present invention relates to an in-vehicle communication system that includes a relay device for a relay of information among different communication buses. In particular, the present invention relates to an in-vehicle communication system capable of properly controlling power supply of the system according to the user's preference while simplifying the configuration of a control device for controlling devices based on information to be relayed.
2. Description of Related Art
In the field of vehicle control, the configuration in which a number of electronic control units (ECU) for respectively controlling devices mounted in a vehicle are connected by communication buses to transmit/receive information mutually for executing various processing is commonly used. Since the number of ECUs connected to a communication bus is limited or a communication speed is varied according to the function of an ECU, a configuration is adopted in which ECUs are divided into a plurality of groups, each of which is connected to a communication bus, and a relay device (gateway) is connected between different communication buses.
With an in-vehicle communication system having a relay device, each communication device transmits an information group with a collection of multiple pieces of information based on a communication protocol, and, between different communication buses, a relay device receives the information group collectively transmitted from each communication device and determines whether or not the information group without modifications thereto is transmitted to another communication bus, to achieve a relay.
Specifically, in an example based on a CAN (Controller Area Network) generally used in the field of an in-vehicle communication system related to vehicle control, FA (Factory Automation) or OA (Office Automation), each ECU stores signal information obtained from devices in the data part of a CAN message identified by CAN ID and collectively transmits the information. A relay device achieves relay processing with a message routing function by referring to, for each of the received CAN messages, a routing table which is stored for each CAN ID and which specifies a communication bus of a relay destination, and by transmitting, as for the CAN message required for a relay, the received CAN message without modification thereto to the communication bus of a relay destination.
Power saving of the whole control system is demanded particularly in the field of vehicle control. Therefore, an in-vehicle communication system including a power management ECU connected to any one of communication buses in an in-vehicle communication system for power supply control such as the distribution of power to in-vehicle devices mounted to a vehicle according to a vehicle state is disclosed.